Ready mix concrete (RMC) is the first choice for projects requiring concrete. The term ‘ready mix’ is used to describe a process where concrete is pre-made at a plant and delivered in batches to job sites. It is a convenient and efficient tool for construction as it is ready to be cast, which saves time and money. Each batch of ready mix concrete is especially created as per the requirements of the contractor. It is prepared with basic ingredients like water, cement, and aggregates and once delivered to the construction site it must be used right away.
Almost all mixing plants have the same basic layout such as an aggregate storage, cement / pozzolan storage, batchers (aggre- gate batching, cement batching, water and admixture batching), dust collection system, feed system, and mixers like a truck mixer or a stationary mixer. Modern technology has enabled operation of ready-mix plants from a remote location, wherein a batch operator uses videos and computers to control crucial areas of the plant.
The process of producing concrete in measured batches is called batching. Every ready-mix concrete plant uses this process to produce concrete. Weigh Batching uses a hopper and a scale to batch all the dry materials. The scale gives a read-out of the weight of material in the hopper. Due to its consistent nature, water can be batched by weigh batching or volumetric batching.
Concrete mixer trucks deliver the pre-made mixture and there is no further preparation required as it’s ready to go at the job site. Ready mix concrete is the preferred choice for both small and large projects and is the ideal solution in any site condition.
Control Room: The ‘brain’ of the plant that calculates and sends out the exact measurements required for each sub-station, allowing them to create the specified mix.
Aggregate Bins: This is where all the different types of aggregates are stored. Here, the exact amount of the required materials is weighed, and then carried via a conveyor belt to the mixing station and ready to be mixed together.
Cement Silos: Here, the cement is stored, weighed, and transferred to the mixing station, ready to be mixed with the aggregates.
Water & Additives: Once water is added to the dry ingredients, the wet concrete mix starts to form. Additives are also added for extra strength, faster curing, or better workability.
The Mixing Station: Here, all the dry ingredients are mixed together with the wet ingredients until the correct consistency is formed.
The Discharge Point: The mixture is discharged and loaded into the back of the drum mixer, which rotates to keep the consistency correct while being transported to the job site.
RMC is being preferred over traditional concrete due to ease of use, greater convenience, economy, and better quality. Furthermore, wastage reduction, low inventory costs, and efficient utilization lead to a lowering of the overall project costs, which in turn will augment the product demand in the coming years. Key benefits of RMC are low labour and supervising cost, consumer awareness regarding eliminating wastage associated with bulk handling, and consistency in quality.
An increase in big projects is spurring consumption of RMC because of its high quality and ease of use. The time constraints placed upon infrastructure development projects in the urbanized economies is creating a high demand for ready-made concrete mixes. Also, RMC has reduced shrinkage, cracking and volume change.
On the downside, concrete’s limited timespan between mixing and going off means that ready-mix should be placed within 90 minutes of batching at the plant. This feature acts as a restraint in the market.
Economic Impact on Industry
An RMC manufacturing company will have the following departments:
- Managerial Board
- Quality Assurance & Quality Control Department
- Operating Department
- Coordination Department
- Mechanical Department
- Electrical Department
Quality Control & Quality Assurance
The QA/QC team is headed by a QA/QC Manager, who is the key person in the decision making process. He is assisted by a QA/QC Incharge whose job is to co-ordinate and implement the quality guidelines and test procedures for the batching plant. The Incharge is assisted by at least two QA/QC engineers who are responsible for physically conducting the tests of the incoming raw materials and the final RMC. They are required to check the proper functioning and calibration of all the equipment and carry out daily or weekly quality monitoring as per the proposed model. The QA/QC Incharge will take decisions on the assignable causes noticed during the monitoring phase.
At least four lab technicians should be employed per plant to carry out the sampling and testing. The fire performance of building products has always come under close scrutiny — and for good reason. The structures where people live and work must be safe. It is for this reason that building codes exist as a means to safeguard life and private and public welfare by regulating the design, construction practices, quality of construction materials, location, occupancy and maintenance of buildings and structures – all of which should be monitored and tested as per the code standards.
The work under a tender should be executed strictly in accordance with the constructional and material requirements defined under the specifications. The contractor must acquaint himself with these specifications to determine his contractual obligations for the work. The conditions of these specifications will be binding on the contractor and no deviation will be permissible, unless specifically approved by the consultant or project-in-charge, in writing. In the absence of any detailed specifications, the latest Indian standard specifications and code of practice will become applicable. Wherever the codes and specifications are absent, then the same will be governed by sound engineering practices and the decision of the project-in-charge / consultant in matters of interpretation etc., will be deemed as final and binding on the contractor.
Tests and relative IS codes for concrete related materials:
Cement Tests IS:4031 – 2019
- Determination of fineness by dry sieving
- Determination of fineness by specific surface by Blaine air permeability method
- Determination of soundness
- Determination of consistency of standard cement paste
- Determination of initial and final setting times
- Determination of compressive strength of hydraulic cement (other than masonry cement)
- Determination of compressive strength of masonry cement
- Determination of transverse and compressive strength of plastic mortar using prism
- Determination of heat of hydration
- Determination of drying shrinkage
- Determination of density
- Determination of air content of hydraulic cement mortar
- Measurement of water retentivity of masonry cement
- Determination of false set
- Determination of fineness by wet sieving Method of chemical analysis of hydraulic cement
- Methods of test for aggregate for concrete particle size and shape
- Methods of test for aggregate for concrete estimation of deleterious materials and organic impurities
- Methods of test for aggregate for specific gravity, density, voids, absorption & bulking
- Methods of test for aggregate for Mechanical properties.
- Methods of test for aggregate Soundness
- Methods of test for aggregate measuring mortar making properties of fine aggregates.
- Methods of test for aggregate for alkali-aggregate reactivity
- Methods of test for aggregate for petrographic examination
- Sampling of fresh concrete
- Determination of consistency of fresh concrete
- Determination of density of fresh concrete
- Making and curing of test specimens
- Tests on fresh self-compacting concrete
- Determination of setting time of concrete by penetration resistance
- Determination of water soluble and acid soluble chlorides in mortar and concrete
- Analysis of freshly mixed concrete
- Compressive, flexural and split tensile strength of hardened concrete
- Properties of hardened concrete other than strength
- Making, curing and determining compressive strength of accelerated cured concrete test specimens
- Sampling, preparing and testing of concrete cores
- Non-destructive testing of hardened concrete
- Determination of drying shrinkage and moisture movement for concrete samples
- Determination of creep of concrete cylinders in compression
- Determination of modulus of elasticity
- Wear Resistance
- Pull out test for bond in reinforced concrete
- Method for determination of Portland cement content of hydraulic cement concrete
- Determination of water soluble and acid soluble chlorides in hardened mortar and concrete
- As it is made by professionals, RMC is of high quality and therefore more sustainable and durable.
- RMC is made by using consistent methods and precise equipment. Materials are tested before usage and the whole process is monitored by professionals to maintain the quality of the mixture.
- As the mixture is made by mechanized operations, the speed of delivery is faster, which means that the whole process of construction will be faster.
- Also, there will no delays in erection and dismantling of the site batching plant.
- Wastage of the ready-mix concrete is less. Proper mixing and better handling of the mixture reduces the consumption of concrete by approx 10%. So, it will reduce the cost of the project.
- Less consumption will reduce production and result in less pollution of the environment.
- As RMC plants use bulk cement, the ratio of dust in cement is reduced.
- Since the mix is more durable, there is increased service life.
- Due to atomized processes, RMC requires less human labour, thus reducing the risk of human errors.
- Fuel (diesel/petrol) usage is less; this reduces the cost of the project, besides reducing noise and air pollution.
- It is very helpful in sites in congested areas.